This invention relates to the armature of a rotating electrical machine and more particularly to the coil winding thereof and the method of forming such winding.
The armature of a rotating electrical machine is generally comprised of a core consisting of a circular core portion from which a plurality of circumferentially spaced teeth radially extend. Coils are wound around these teeth and cooperate with circumferentially spaced permanent magnets. Such constructions are employed in both electric motors and generators.
Generally the coils are wound around the pole teeth by feeding a wire in looping fashion around the pole teeth. The wire is fed from a feeding needle that is extended into the space between the adjacent teeth and the needle is passed in a circular fashion around the pole tooth and the wire is deposited thereon in coils. As the winding continues the needle is gradually moved along the length of the tooth so that it is fully wound.
The resulting structure is shown in FIG. 1 which is a partial view of an armature being wound in the conventional prior are method. The armature is indicated generally by the reference numeral 21 and has a ferromagnetic core consisting of a circular ring portion 22 from which pole teeth 23 radially extend. The core is preferably formed from a plurality of laminated sheets. The pole teeth 23 are circumferentially spaced to define gaps 24 therebetween. The ends of these pole teeth are formed with projections 25 to define a narrow mouth 26 opening into the gap 24.
A winding needle 27 is passed into the gap 24 through the mouths 26 and feeds a wire 28 around an insulating bobbin (not shown) that encircles each pole tooth 23. As the needle 27 is passed around the pole teeth in a circular pattern the wire is looped onto the pole teeth 23 to form the coils, indicated generally at 29.
Thus it is clear that the number of turns around each pole tooth 23 is limited due to the necessity of providing clearance for the needle. To overcome this disadvantage and to permit greater winding density, inventors of the assignee hereof have proposed a construction as disclosed in U.S. Pat. No. 6,590,310, issued Jul. 8, 2003, entitled xe2x80x9cSTATOR COIL STRUCTURE FOR REVOLVING-FIELD ELECTRICAL MACHINE AND METHOD OF MANUFACTURING SAMExe2x80x9d. Certain inventors hereof have also invented several improvements thereon presently pending.
These inventions either eliminate totally or minimize the projection of the winding needle into the slot during winding. This is accomplished by providing an insulating projection on one or both radially extending, axially spaced faces of the pole teeth. The wire end is restrained at an end of the pole tooth and as the winding occurs the wire is caused to slide along the pole tooth until it is stopped by contact with the ring portion of the armature of the previous coil winding. In this way the coils pile up and it is possible for the windings on one pole tooth to fill nearly all of area on one side of the gap between adjacent pole teeth. The remainder of the gap is nearly filled by the winding around the adjacent pole tooth.
Although these inventions greatly improve the winding density, there can be further improvement. For example, with those inventions there is a possibility of interference between adjacent windings in the area of the slot causing the possibility of damage to the insulation of the winding and/or the winding may bulge out of the mouth of the slot. Thus some clearance is provided.
It is, therefore, a principle object of this invention to provide an armature construction and winding method that permits greater coil density.
A first feature of the invention is adapted to be embodied in an electrical armature comprised of a core having a plurality of pole teeth extending radially from a circular ring portion. A plurality of winding coils each encircle a respective one of the pole teeth. The coil windings on adjacent of the pole teeth are wound such that the radial extent of the windings relative to an axis of the respective pole tooth is not the same at all positions along the length of the pole tooth axis. The radially outermost winding of at least one of the adjacent pole teeth extends across an axially extending plane positioned equidistant between the adjacent pole teeth.
Another feature of the invention is adapted to be embodied in a method of winding an electrical armature. The armature is comprised of a core having a plurality of pole teeth extending radially from a circular ring portion. The method comprises winding an electric wire around a first of said pole teeth to form a plurality of winding coils the radial extent of which relative to an axis of the respective pole tooth is not the same at all positions along the length of the wound pole tooth axis so that the radially outermost winding extends across an axially extending plane positioned equidistant between adjacent pole teeth.